Graft polymer dispersion having a third monomer and polyurethane foams having a reduced tendency to shrink prepared thereby

ABSTRACT

There is a provided a stable low viscosity graft polymer dispersion comprising from 25 to 60 weight percent based on the total weight of the polymer dispersion of at least three ethylenically unsaturated monomers polymerized in the presence of a reaction moderator and a free radical initiator in a polyol mixture initially containing less than 0.1 moles of induced unsaturation per mole of said polyol mixture. One of the monomers in the mixture of ethylenically unsaturated monomers is a hydroxylfunctional or aminofunctional C 2  -C 6  alkyl methacrylate.

This application is a division of application Ser. No. 09/016,660, filedJan. 30, 1998, now U.S. Pat. No. 5,863,959, which is a division ofapplication Ser. No. 08/520,911, filed Aug. 30, 1995, now U.S. Pat. No.5,741,851, which is a continutation of application Ser. No. 08/184,730,filed Jan. 21, 1994, now abandoned.

FIELD OF THE INVENTION

This invention pertains to graft polymer dispersions having a particularthird ethylenically unsaturated monomer added to the monomer mixture.Water blown molded polyurethane foams prepared with this graft polymerdispersion exhibit little or no shrinkage.

BACKGROUND OF THE INVENTION

A common problem encountered with molded polyurethane foams blown withwater, especially high quantities of water exceeding 3.0 weight percentbased on the total weight of the polyol composition, is that the foamwill drastically shrink unless crushed with mechanical means while hot.Efforts have been made to chemically manipulate the polyurethane foamsystem to obviate the need for mechanical crushing means. The variousattempts made to reduce foam shrinkage included using low activitysurfactants, reducing the amount of ethylene oxide termination on thepolyether polyol to slow its reactivity, or using a graft polymerdispersion prepared by the continuous process rather than by thesemi-batch process. A wider particle size distribution is thought to aidin opening up more cells in the foam, which in turn reduces foamshrinkage. It is desirable, however, to obtain a polyurethane foam byusing a graft polymer dispersion which is effective to reduce foamshrinkage without regard to its particle size distribution or its methodof manufacture.

SUMMARY OF THE INVENTION

It is an object of the invention to obtain a water blown polyurethanefoam exhibiting little or no shrinkage upon demold. It is also an objectof the invention to use a graft polymer dispersion to effect a reductionin foam shrinkage prepared by a semi-batch or continuous method. It is afurther object of the invention that this graft polymer dispersion havea high solids content, is stable, and has a low viscosity.

These objects have been met by incorporating a third ethylenicallyunsaturated monomer into the monomer mixture in the graft polyoldispersion. In particular, the graft polymer dispersion of the inventioncomprises from 25 to 60 weight percent, based on the total weight of thepolymer dispersion, of a mixture of at least three ethylenicallyunsaturated monomers polymerized in the presence of a reaction moderatorand a free radical initiator in a polyol mixture initially containingless than 0.1 moles of induced unsaturation per mole of said mixture,wherein at least one monomer in said mixture of ethylenicallyunsaturated monomers comprises a hydroxylfunctional oraminofunctional(2-(6-alkyl methacrylate. Molded polyurethane foamsmanufactured from this graft polymer dispersion are dimensionally stableand exhibit little or no shrinkage.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, there is provided a mixture of atleast three ethylenically unsaturated monomers polymerized in thepresence of an effective amount of free radical initiator and a reactionmoderator in an unsaturated polyol mixture having initially less than0.1 moles of induced unsaturation per mole of polyol mixture; andpreferably, the polyol mixture employs as part of the mixture apolyetherester polyol prepared by the reaction of a polyoxyalkylenepolyether polyol with maleic anhydride and an alkylene oxide. Thepolyetherester polyol may be isomerized by methods well known to thoseskilled in the art. These include beat or isomerization catalysts suchas morpholine, dibutylamine, diethylamine, diethanolamine, thiols andsalts and oxides of divalent metals. The polyols having inducedunsaturation in the polyol mixture are referred to as "macromers."

The graft polymer dispersion of the invention employs at least threeethylenically unsaturated monomers, at least one of which is ahydroxylfunctional or aminofunctional C₂ -C₆ alkyl methacrylate. Thealkyl group may comprise two to six carbon atoms in the alkyl chainwhich may be branched with primary or secondary hydroxylfunctionalities, or primary, secondary, tertiary amino functionalities.Suitable examples of the alkyl methacrylate employed in the mixture ofethylenically unsaturated monomers are 2-hydroxyethyl-methacrylate,hydroxypropyl methacrylate, hydroxybutyl methacrylate, anddimethylaminoethyl methacrylate, with 2-hydroxyethyl methacrylate (HEMA)and dimethylaminoethyl methacrylate (DMAEMA) being most preferred.

The amount of the alkyl methacrylate monomer employed is an amounteffective to produce a water blown polyurethane foam which has reducedshrinkage upon demold in comparison with the same foam made without thealkyl methacrylate. It is preferred that the foam produced by the graftpolymer dispersion of the invention be dimensionally stable, and by"stable" it is meant a molded uncrushed foam which at 25° C. measuresless than 3 mm from the deepest point of depression in the foam block tothe bottom of a straight edge placed across the opposite corners of anyside of the foam. It is more preferable that the foam is one whichmeasures less than 1 mm, most preferably one which measures 0 mm. Theamount of alkyl methacrylate may range from 5 weight percent to lessthan 50 weight percent based on the total weight of ethylenicallyunsaturated monomers present, and is preferentially present in amountsof from 10 weight percent to 25 weight percent. At these concentrations,one obtains a stable high water blown polyurethane foam which preferablyexhibits no shrinkage at all.

The other two monomers in the monomer mixture are suitably any of thewell-known ethylenically unsaturated monomers employed in the art.Representative ethylenically unsaturated monomers which may be employedin the present invention include butadiene, isoprene, 1,4-pentadiene,1,6-hexadiene, 1,7-octadiene, styrene, α-methylstyrene, 2-methylstyrene,3-methylstyrene, and 4-methylstyrene, 2,4-dimethylstyrene, ethylstyrene,isopropylstyrene, butylstyrene, and the like; substituted styrenes suchas cyanostyrene, nitrostyrene, N,N-dimethylaminostyrene, acetoxystyrene,methyl 4-vinylbenzoate, phenoxystyrene, p-vinylphenyl oxide, and thelike; the acrylic and substituted acrylic monomers such asacrylonitrile, acrylic acid, methacrylic acid, methyl acrylate,2-hydroxyethyl acrylate, methyl methacrylate, cyclohexyl methacrylate,benzyl methacrylate, isopropyl methacrylate, octyl methacrylate,methacrylonitrile, ethyl α-ethoxyacrylate, methyl α-acetaminoacrylate,butyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, phenylmethacrylate, N,N-dimethylacrylamide, N,N-dibenzylacrylamide,N-butylacrylamide, methacrylyl formamide, and the like; the vinyl esterssuch as vinyl acetate, vinyl butyrate, isopropenyl acetate, vinylformate, vinyl acrylate, vinyl methacrylate, vinyl methoxyacetate, vinylbenzoate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether,vinyl propyl ethers, vinyl butyl ethers, vinyl 2-ethylhexyl ether, vinylphenyl ether, vinyl 2-methoxyethyl ether, methoxybutadiene, vinyl2-butoxyethyl ether, 3,4-dibydro-1,2-pyran, 2-butoxy-2'-vinyloxydiethylether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone,vinyl phenyl ketone, vinyl ethyl sulfone, N-methyl-N-vinyl acetamide,N-vinyl-pyrrolidone, vinyl imidazole, divinyl sulfoxide, divinylsulfone, sodium vinylsulfonate, methyl vinylsulfonate, N-vinyl pyrrole,vinyltoluene, vinylnaphthalene, and the like; dimethyl fumarate,dimethyl maleate, maleic acid, crotonic acid, fumaric acid, itaconicacid, monomethyl itaconate, t-butylaminoethyl methacrylate, glycidylacrylate, allyl alcohol, glycol monoesters of itaconic acid, vinylpyridine, and the like. Preferably, the other two monomers areacrylonitrile and styrene. More than a total of three monomers may becharged. A fourth or fifth monomer may be added to the mixture of thethree monomers.

The amount of ethylenically unsaturated monomer mixture employed in thepolymerization reaction is generally from 25 percent to 60 percent,preferably from 25 percent to about 50 percent, based on the totalweight of the polymer dispersion. The polymerization occurs at atemperature between about 25° C. and 180° C., preferably from 80° C. to135° C. It is preferred that at least 40 to 80 weight percent, based onthe total weight of the monomer mixture, of the monomer employed isstyrene or 4-methylstyrene. It is more preferred that the amount of eachmonomer is from 10 weight percent to 25 weight percent of the alkylmethacrylate such as HEMA or DMAEMA, 40 weight percent to 60 weightpercent styrene, and 25 weight percent to 40 weight percentacrylonitrile, based on the total weight of the monomer mixture.

The monomers may be added as separate charges to a reaction chamber, ormay be added as one or two mixed charges. For example, the styrene andalkyl methacrylate monomers may be added to the reaction chamber as amixed charge along with a separate acrylonitrile charge.

In another embodiment, styrene, acrylonitrile, and the alkylmethacrylate monomers may be premixed and added to the reaction vesselas a single charge. By mixture of monomers is meant that at least threemonomers are reacted, irrespective of the method of charging employed.

The polyol mixture to which the monomers are added comprises a macromerand carrier polyol, and polymerization proceeds in the presence of apolymerization initiator and a reaction moderator. The macromer may beprepared separately by reacting in the presence of an isomerizationcatalyst, a conventional polyol essentially free from ethylenicunsaturation with an organic compound having both ethylenic unsaturationand a hydroxyl, carboxyl, anhydride, isocyanate, or epoxy group; or theymay be prepared by reacting the organic compound having both ethylenicunsaturation and a hydroxyl, carboxyl, anhydride, isocyanate, or epoxygroup as a reactant in the preparation of the conventional polyol.

Representative conventional polyols essentially free from ethylenicunsaturation which may be employed in the preparation of macromers andwhich are also independently employed as the carrier polyol are wellknown to those skilled in the art. They are often prepared by thecatalytic condensation of an alkylene oxide or mixture of alkyleneoxides either simultaneously or sequentially with an organic compoundhaving at least two active hydrogen atoms, such as evidenced by U.S. PatNos. 1,922,459; 3,190,927; and 3,346,557. Representative polyols includepolyhydroxyl-containing polyesters, polyoxyalkylene polyether polyols,polyhydroxy-terminated polyurethane polymers, polyhydroxyl-containingphosphorus compounds, and alkylene oxide adducts of polyhydricpolythioesters, polyacetals, aliphatic polyols and thiols, ammonia, andamines including aromatic aliphatic, and heterocyclic amines, as well asmixtures thereof. Alkylene oxide adducts of compounds which contain twoor more different groups within the above-defined classes may also beused, for example, amino alcohols which contain an amino groups and ahydroxyl group. Also, alkylene oxide adducts of compounds which containone SH group and one OH group as well as those which contain an aminogroup and an SH group may be used. Generally, the equivalent weight ofthe polyols essentially free from ethylenic unsaturation used to preparethe macromer and independently used as the carrier polyol will vary from100 to 10,000, preferably from 1,000 to 3,000.

Any suitable hydroxy-terminated polyester may be used such as areprepared, for example, from polycarboxylic acids and polyhydricalcohols. Any suitable polycarboxylic acid may be used such as oxalicacid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelicacid, suberic acid, azelaic acid, sebacic acid, brassylic acid, thapsicacid, maleic acid, fumaric acid, glutaconic acid, α-hydromuconic acid,β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α,β-diethylsuccinicacid, isophthalic acid, terephthalic acid, phthalic acid, hemimelliticacid, and 1,4-cyclohexanedicarboxylic acid. Any suitable polyhydricalcohol may be used such as ethylene glycol, propylene glycol,dipropylene glycol, trimethylene glycol, 1,2-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, hydroquinone,resorcinol glycerol, glycerine, 1,1,1-trimethylol-propane,1,1,1-trimethylolethane, pentaerythritol, 1,2,6-hexanetriol, α-methylglucoside, sucrose, and sorbitol. Also included within the term"polyhydric alcohol" are compounds derived from phenol such as2,2-bis(4-hydroxyphenyl)-propane, commonly known as Bisphenol A.

The hydroxyl-containing polyester may also be a polyester amide such asis obtained by including some amine or amino alcohol in the reactantsfor the preparation of the polyesters. Thus, polyester amides may beobtained by condensing an amino alcohol such as ethanolamine with thepolycarboxylic acids set forth above or they may be made using the samecomponents that make up the hydroxyl-containing polyester with only aportion of the components being a diamine such as ethylene diamine.

Any suitable polyoxyalkylene polyether polyol may be used such as thepolymerization product of an alkylene oxide or a mixture of alkyleneoxides with a polyhydric alcohol. Any suitable polyhydric alcohol may beused such as those disclosed above for use in the preparation of thehydroxy-terminated polyesters. Any suitable alkylene oxide may be usedsuch as ethylene oxide, propylene oxide, butylene oxide, amylene oxide,and mixtures of these oxides. The polyoxyalkylene polyether polyols maybe prepared from other starting materials such as tetrahydrofuran andalkylene oxide-tetrahydrofuran mixtures; epihalohydrins such asepichlorohydrin; as well as aralkylene oxides such as styrene oxide. Thepolyoxyalkylene polyether polyols may have either primary or secondaryhydroxyl groups. Included among the polyether polyols arepolyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol,polytetramethylene glycol, block copolymers, for example combinations ofpolyoxypropylene and polyoxyethylene poly-1,2-oxybutylene andpolyoxyethylene polyols, poly-1,4-tetramethylene and polyoxyethylenepolyols, and copolymer polyols prepared from blends or sequentialaddition of two or more alkylene oxides. The polyalkylene polyetherpolyols may be prepared by any known process such as, for example, theprocess disclosed by Wurtz in 1859 and Encyclopedia of ChemicalTechnology, Vol. 7, pp. 257-262, published by Interscience Publishers,Inc. (1951) or in U.S. Pat. No. 1,922,459. Polyethers which arepreferred include the alkylene oxide addition products oftrimethylolpropane, glycerine, pentaerythritol, sucrose, sorbitol,propylene glycol, and 2,2'-(4,4'-hydroxyphenyl)propane and blendsthereof having equivalent weights of from 100 to 10,000.

Suitable polyhydric polythioethers which may be condensed with alkyleneoxides include the condensation product of thiodiglycol or the reactionproduct of a dicarboxylic acid such as is disclosed above for thepreparation of the hydroxyl-containing polyesters with any othersuitable thioether glycol.

Polyhydroxyl-containing phosphorus compounds which may be used includethose compounds disclosed in U.S. Pat. No. 3,639,542. Preferredpolyhydroxyl-containing phosphorus compounds are prepared from alkyleneoxides and acids of phosphorus having a P₂ O₅ equivalency of from about72 percent to about 95 percent.

Suitable polyacetals which may be condensed with alkylene oxides includethe reaction product of formaldehyde or other suitable aldehyde with adihydric alcohol or an alkylene oxide such as those disclosed above.

Suitable aliphatic thiols which may be condensed with alkylene oxidesinclude alkanethiols containing one or two -SH groups such as2-mercaptoethanol, 1,2-ethanedithiol, 1,2-propanedithiol,1,3-propanedithiol, and 1,6-hexanedithiol; alkene thiols such as2-butene-1,4-dithiol; and alkyne thiols such as 3-hexyne-1,6-dithiol.

Suitable amines which may be condensed with alkylene oxides includearomatic amines such as aniline, o-chloroaniline, p-aminoaniline,1,5-diarninonaphthalene, methylene dianiline, the condensation productsof aniline and formaldehyde, and 2,3-, 2,6-, 3,4-, 2,5-, and2,4-diaminotoluene; aliphatic amines such as methylamine,triisopropanolamine, ethylenediamine, 1,3-diaminopropane,1,3-diaminobutane, 1,4-diaminobutane, and ammonia.

Also, polyols containing ester groups can be employed in the subjectinvention. These polyols are prepared by the reaction of an alkyleneoxide with an organic dicarboxylic acid anhydride and a compoundcontaining reactive hydrogen atoms. A more comprehensive discussion ofthese polyols and their method of preparation can be found in U.S. Pat.Nos. 3,585,185; 3,639,541; and 3,639,542.

The induced unsaturated polyols, or macromers, which are employed in theinvention may be prepared by reacting the above-mentioned conventionalpolyols with a compound having both ethylenic unsaturation and ahydroxyl, carboxyl, anhydride, isocyanate, or epoxy group.Representative of such organic compounds include mono- andpolycarboxylic acids and anhydrides such as maleic acid and maleicanhydride, fumaric acid, crotonic acid and anhydride, propenyl succinicanhydride, acrylic acid, acryoyl chloride, hydroxyethyl acrylate ormethacrylate or halogenated maleic acids and anhydrides, unsaturatedpolyhydric alcohols such as 2-butene-1,4-diol, glycerol allyl ether,trimethylolpropane allyl ether, pentaerythritol allyl ether,pentaerythritol vinyl ether, pentaerythritol diallyl ether, and1-butene-3,4-diol, unsaturated epoxides such as1-vinyl-cyclohexene-3,4-epoxide, butadiene monoxide, vinyl glycidylether(1-vinyloxy-2,3-epoxy propane), glycidyl methacrylate and3-allyloxypropylene oxide (allyl glycidyl ether), and the aryl orarylaliphatic isocyanates disclosed in U.S. Pat. No. 5,093,412,incorporated herein by reference, such as1-(t-butylisocyanato)-3-isopropenylbenzene, which are believed to havethe advantage of shorter reaction times and yield macromers and polyoldispersions having lower viscosities than macromers and polyoldispersions prepared with other of the aforementioned compounds havingboth ethylenic unsaturation and a hydroxyl, carboxyl, anhydride, orepoxy group. If a polycarboxylic acid or anhydride is employed toincorporate unsaturation into the polyols, it is preferable to react theunsaturated polyol with an alkene oxide, preferably ethylene orpropylene oxide, to replace the carboxyl groups with hydroxyl groupsprior to employment in the present invention. The amount of alkyleneoxide employed is such as to reduce the acid number of the unsaturatedpolyol to about 5 or less.

The alkylene oxides which may be employed for the preparation of thepolyetherester polyols include ethylene oxide, propylene oxide, butyleneoxide, amylene oxide, and mixtures of these oxides, preferably ethyleneand propylene oxide.

The maleated macromers are isomerized at temperatures ranging from 80°C. to 120° C. for one-half hour to three hours in the presence of aneffective amount of an isomerization catalyst. The catalyst is employedat concentrations greater than 0.01 weight percent based on the weightof the macromer and may be as high as 5.0 weight percent.

When preparing the polyetherester polyol employing the catalyst selectedfrom the group consisting of salts and oxides of divalent metals, theconcentration of catalyst which may be employed ranges from 0.01 to 0.5weight percent, based on the weight of polyol mixture. The temperaturesemployed range from 75° C. to 175° C.

Among the divalent metals which may be employed are zinc acetate, zincchloride, zinc oxide, zinc neodecanoate, tin chloride, calciumnaphthenate, calcium chloride, calcium oxide, calcium acetate, coppernaphthenate, cadmium acetate, cadmium chloride, nickel chloride,manganese chloride, manganese acetate, and cobalt naphthenate.

Certain of the above-mentioned catalysts such as calcium naphthenatepromote the complete isomerization of the maleate to the fumaratestructure during the preparation of the macromer, while others such aszinc chloride, which is an effective catalyst for the esterification,inhibit this isomerization.

The macromer unsaturation ranges from 0.1 mole to 1.5 mole ofunsaturation per mole of the conventional polyol and, preferably, from0.5 to 1.0 mole of unsaturation per mole of conventional polyol.

The process of the invention comprises reacting a mixture of monomerswith a polyol mixture comprised of carrier polyol and macromer, in thepresence of a polymerization initiator and a reaction moderator. Thisprocess may be carried out by the continuous or semi-batch method, as isdisclosed in U.S. Pat. Nos. 4,454,255; 4,458,038; 4,661,531; 4,689,354;and 4,690,956; all of which are incorporated herein by reference. In thecontinuous method, a first continuous stream comprised of the mixture ofmonomers and reaction moderator is combined in a reaction vessel with asecond continuous stream comprised of a carrier polyol, the macromer,the polymerization initiator, and optionally reaction moderator;reacted; and withdrawn from the reaction vessel on a continuous basis.In the semi-batch process, a first stream of the mixture of monomers iscombined with a second stream comprising the carrier polyol, thepolymerization initiator, and the reaction moderator in a reactionvessel containing more carrier polyol, the macromer, and more reactionmoderator; allowed to react; and withdrawn from the reaction vessel oncethe reaction proceeds to completion. Thus, as can be seen by thedifference between the two reaction methods, not all of the polyolmixture ingredients need be mixed into one stream prior to combiningwith the monomer mixture stream. The polyol mixture ingredients may besplit up between a feed stream and the reaction vessel as in thesemi-batch process. Further, the reaction moderator may be divided upbetween the two streams and the reaction vessel or any combination ofthese. However, the monomer mixture and the polymerization initiator arekept in separate streams to avoid premature polymerization of themixture of monomers. Whichever method is employed, however, ultimatelythe mixture of monomers are polymerized in a polyol mixture comprised ofconventional polyols essentially free of ethylenic unsaturation (thecarrier polyol) and a macromer, in the presence of a reaction moderatorand a polymerization initiator.

To initiate polymerization among the at least three monomers, any one ofthe well-known free radical polymerization initiators are employed.Examples include the peroxides, persulfates, perborates, percarbonates,azo compounds, etc. These include hydrogen peroxide, dibenzoyl peroxide,acetyl peroxide, benzoyl hydroperoxide, t-butyl hydroperoxide,di-t-butyl peroxide, lauroyl peroxide, butyryl peroxide,diisopropylbenzene hydroperoxide, cumene hydroperoxide, p-menthanehydroperoxide, diacetyl peroxide, di-α-cumyl peroxide, dipropylperoxide, diisopropyl peroxide, isopropyl-t-butyl peroxide,butyl-t-butyl peroxide, difuroyl peroxide, bis(triphenylmethyl)peroxide, bis(p-methoxybenzoyl) peroxide, p-monomethoxybenzoyl peroxide,rubene peroxide, ascaridol, t-butyl peroxybenzoate, diethylperoxyterephthalate, propyl hydroperoxide, isopropyl hydroperoxide,n-butyl hydroperoxide, t-butyl hydroperoxide, cyclohexyl hydroperoxide,trans-decalin hydroperoxide, α-methylbenzyl hydroxperoxide,α-methyl-α-ethyl benzyl hydroperoxide, tetralin bydroperoxide,triphenylmethyl hydroperoxide, diphenylmethyl hydroperoxide,α,α'-azobis-(2-methyl heptonitrile), 1-t-butylazo-1-cyanocyclohexane,persuccinic acid, diisopropyl peroxy dicarbonate,2,2'-azobis(2,4-dimethylvaleronitrile),2-t-butylazo-2-cyano4-methoxy-4-methylpentane,2,2'-azo-bis-2-methylbutanenitrile, 2-t-butylazo-2-cyanobutane,1-t-amylazo-1-cyanocyclohexane,2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile),2,2'-azobis-1-methylbutyronitrile, 2-t-butylazo-2-cyano-4-methylpentane,2-t-butylazo-2-isobutyronitrile, butylperoxyisopropyl carbonate and thelike; a mixture of initiators may also be used. The preferred initiatorsare 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(isobutyronitrile),2,2'-azobis(2,4-dimethylvaleronetrile),2-t-butylazo-2-cyano-4-methoxy4-methyl pentane,2-t-butylazo-2-cyano-4-methylpentane, 2-t-butylazo-2-cyano-butane andlauroyl peroxide, Generally, from about 0.1 percent to about 10 percent,preferably from about 0.2 percent to about 2 percent, by weight ofinitiator based on the weight of the monomer will be employed in theprocess of the invention.

Materials commonly known as chain transfer agents to those skilled inthe art are preferentially employed as reaction moderators. Although thechain transfer agents do reduce the molecular weight of the vinylpolymer formed, certain chain transfer agents also perform a function indispersion polymerization not previously recognized in the art. Combinedwith the other components of this invention, these reaction moderatorsgive lower viscosity, stable dispersions. In the absence of a reactionmoderator, the dispersions of this invention have a higher viscosity,may settle or coagulate, and the vinyl polymer portion is not soluble ingood solvents like N,N-dimethylformamide. The polymerization reactionmay be carried out at temperatures between 25° C. and 180° C.,preferably between 80° C. and 135° C. The polyol mixture containsinitially less than 0.1 mole of induced unsaturation per mole of polyolmixture and ranges from 0.001 to 0.09 mole of unsaturation per mole ofpolyol, and preferably 0.002 to 0.02 mole of induced unsaturation permole of polyol mixture.

Among those reaction moderators which may be employed are as follows:acetaldehyde, N,N-dimethylacetamide, acrolein, bis(2-ethoxyethyl)acetal,aniline, N,N-dimethylaniline, N,N-diethylaniline, anthracene, arabinose,2-butanone, ethyl benzene, 1,4-butanediol, iodobenzene, vinyl benzoate,p-benzoquinone, 1-buten-3-yne, 1-butanol, carbon tetrabromide,chloroform, copper sulfate, crotonaldehyde, cumene, ethylene glycol,allyl alcohol, 2-vinyl-1,3-dioxolane, methyl-α-D-glycoside,glyceraldehyde, glycerol, 1,5hexadien-3-yne, ferric chloride, isobutylalcohol, methyl amine, 2,6-dimethyl-2,6-octadiene, 4-methyl-1-pentanol,1-methyl piperidine, toluene, tributylamine, triethylamine,trimethylamine, tripropylamine, diphenylamine, 2-mercaptoethanol,1-propanol, 2-octanol, 2-ethyl-1-hexanol,4,4'-Bis(α,α-dimethylbenzyl)diphenylamine; and preferably 2-pentanol,thiophenol, 2-butanol, morpholine, 2-propanol, bromotrichloromethane,1-dodecanethiol, and tertiary dodecyl mercaptan. The reaction moderatorsare not limited to those listed above.

The reaction moderators employed will depend on the particular mixturesof monomers employed and the molar ratios of such mixtures. Theconcentration of the reaction moderator is that amount which iseffective in producing low viscosity stable dispersions and may rangefrom 0.1 weight percent to 30 percent by weight based on the weight ofmonomer, preferably from 0.5 to 10.0 weight percent based on the weightof monomer.

The graft polymer dispersion of this invention have useful viscositiesless than 10,000 cps at 25° C. Preferably, they have viscosities rangingfrom 2,000 to 8,000 cps at 25° C., more preferably, from 2,000 cps to5,000 cps at 25° C.

The water-blown polyurethane foams employed in the present invention aregenerally prepared by the reaction of a graft polymer dispersion with anorganic polyisocyanate in the presence of water as a blowing agent andoptionally in the presence of additional polyhydroxyl-containingcomponents, chain-extending agents, catalyst, surface-active agents,stabilizers, dyes, fillers, and pigments. Suitable processes for thepreparation of cellular polyurethane plastics are disclosed in U.S.Reissue Pat. No. 25,514, together with suitable machinery to be used inconjunction therewith. When water is added as the blowing agent,corresponding quantities of excess isocyanate to react with the waterand produce carbon dioxide may be used. It is possible to proceed withthe preparation of the polyurethane plastics by a prepolymer techniquewherein an excess of organic polyisocyanate is reacted in a first stepwith the polyol of the present invention to prepare a prepolymer havingfree isocyanate groups which is then reacted in a second step with waterand/or additional polyol to prepare a foam. Alternatively, thecomponents may be reacted in a single working step commonly known as the"one-shot" technique of preparing polyurethanes.

The graft polymer dispersions may also be employed in the preparation ofpolyurethane elastomers.

Organic polyisocyanates which may be employed include aromatic,aliphatic, and cycloaliphatic polyisocyanates and combinations thereof.Representative of these types are the diisocyanates such as m-phenylenediisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate,mixtures of 2,4- and 2,6-toluene diisocyanate, hexamethylenedisocyanate, tetramethylene diisocyanate, cyclohexane-1,4-diisocyanate,hexahydrotoluene diisocyanate (and isomers),naphthalene-1,5-diisocyanate, 1-methoxyphenyl-2,4-diisocyanate,4,4'-diphenylmethane diisocyanate, mixtures of 4,4'- and2,4'-diphenylmethane diisocyanate, 4,4'-biphenylene diisocyanate,3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl4,4'-biphenyldiisocyanate and 3.3'-dimethyldiphenylmethane-4,4'-diisocyanate; thetriisocyanates such as 4,4,4'-triphenylmethane triisocyanate, andtoluene 2,4,6-triisocyanate; and the tetraisocyanates such as4,4'-dimethyldiphenylmethane-2,2'-5,5'-tetraisocyanate and polymericpolyisocyanates such as polymethylene polyphenylene polyisocyanate, andmixtures thereof. Especially useful due to their availability andproperties are 4,4'-diphenylmethane diisocyanate, polymethylenepolyphenylene polyisocyanate, or mixtures thereof for rigid foams, or amixture of the foregoing with toluene dilsocyanates for semi-rigidfoams.

Crude polyisocyanates may also be used in the compositions of thepresent invention, such as crude toluene diisocyanate obtained by thephosgenation of a mixture of toluenediamines or crude diphenylmethaneisocyanate obtained by the phosgenation of crude diphenylmethanediamine. The preferred or crude isocyanates are disclosed in U.S. Pat.No. 3,215,652.

As mentioned above, the graft polyols may be employed along with anotherpolyhydroxyl-containing component commonly employed in the art. Any ofthe polyhydroxyl-containing components which are described above for usein the preparation of the graft polyols may be employed in thepreparation of the polyurethane foams useful in the present invention.

Chain-extending agents which may optionally be employed in thepreparation of the polyurethane foams include those compounds having atleast two functional groups bearing active hydrogen atoms, andpreferably having molecular weights of less than 400, more preferablyless than 300, such as water, hydrazine, primary and secondary dianines,amino alcohols, amino acids, hydroxy acids, glycols, or mixturesthereof. A preferred group of chain-extending agents includes water,ethylene glycol, 1,3-propanediol, 1,10-decanediol, dihydroxycyclohexane,diethylene glycol, 1,6-hexanediol, glycerine, trimethylol propane,1,2,4- 1,3,5-trihydroxycyclohexane, bis(2-hydroxyethyl) hydroquinone,1,4-butanediol and primary and secondary diamines which react morereadily with a prepolymer than does water such as phenylene diamine,1,4-cyclohexane-bis-(methylamine), ethylenediamine, diethylenetriamine,N-(2-hydroxypropyl)ethylenediamine,N,N'-di(2-hydroxypropyl)ethylenediamine, piperazine, and2-methylpiperazine.

The amount of water employed as a blowing agent is effective to producethe desired foam density, preferably from 1 weight percent to 8 weightpercent, based on the total weight of the polyol composition, morepreferably from 3 weight percent to 5 weight percent. The density of thewater-blown foams varies widely, but for most applications is from 2 pcfto 6 pcf, more preferably from 2 pcf to 4 pcf. Other volatilehydrocarbon blowing agents and HCFCs may be admixed with the water ifdesired such as butane, pentane, cyclopentane, hexane, cyclohexane, andthe HCFCs having a ozone-depleting potential of less than 0.05.

Any suitable catalyst may be used, including tertiary amines, such astriethylenediamine, N-methylmorpholine, N-ethylmorpholine,diethylethanolamine, N-cocomorpholine,1-methyl4-dimethylaminoethylpiperazine,3-methoxypropyldimethylamine,N,N,N'-trimethylisopropyl propylenediamiane,3-diethylaminopropyldiethylaamine, di-methylbenzylamine, and the like.Other suitable catalysts are, for example, stannous chloride, dibutyltindi-2-ethyl hexanoate, stannous oxide, as well as other organometalliccompounds such as are disclosed in U.S. Pat. No. 2,846,408.

A surface-active agent is generally necessary for production of highgrade polyurethane foam according to the present invention, since in theabsence of same, the foarns collapse or contain very large uneven cells.Numerous surface-active agents have been found satisfactory. Nonionicsurface active agents are preferred. Of these, the nonionicsurface-active agents such as the well-known silicones have been foundparticularly desirable. Other surface-active agents which are operative,although not preferred, include polyethylene glycol ethers of long chainalcohols, tertiary amine or alkanolamine salts of long chain alkyl acidsulfate esters, alkyl sulfonic esters, and alkyl arylsulfonic acids.

Among the flanmes retardants which may be employed arepentabromodiphenyl oxide, dibromopropanol,tris(β-chloropropyl)phosphate, 2,2-bis(bromoethyl)1,3-propanediol,tetrakis(2-chloroethyl)ethylene diphosphate,tris(2,3-dibromopropyl)phosphate, tris(8-chloroethyl)-phosphate,tris(1,2-dichloropropyl)phosphate,bis-(2-chloroethyl)2-chloroethylphosphonate, molybdenum trioxide,ammonium molybdate, ammonium phosphate, pentabromodiphenyloxide,tricresyl phosphate, hexabromocyclododecane, melamine anddibromoethyl-dibromocyclohexane. The concentrations of flame retardantcompounds which may be employed range from 1 to 25 parts per 100 partsof polyol mixture.

The nature of the invention is illustrated through the followingnon-limiting examples. All parts are by weight unless otherwisespecified.

Polyol A is a trimethylolpropane initiated polyoxypropylenepolyoxyethylene polyether polyol terminated with 15 weight percentpolyoxyethylene groups and having a nominal OH number of 25.

Macromer A is Polyol A containing 0.5 moles of fumarated unsaturationprepared by employing Procedure A.

Polyol B is a 31 weight percent 1:2 acrylonitrile:styrene graft polyolwith Polyol C as the carrier, and having a Brookfield viscosity of about3240 mPas at 25° C.

Polyol C. is a glycerine initiated propylene oxide adduct terminatedwith 18.5 weight percent of polyoxyethylene groups and having a nominalOH number of 35.

Polyol D is a trirnethylolpropane initiated propylene oxide adducthaving about 13 weight percent terminal polyoxyethylene groups and anominal OH number of 35.

Polyol E is a 93/7 parts by weight blend of Polyol C and glycerine,respectively.

Polyol F is a glycerine initiated ethylene oxide/propylene oxideheteric-block adduct with 10 weight percent of ethylene oxide added into form a heteric adduct, and capped with 5 weight percent ethyleneoxide, the polyol having a nominal OH number of 25.

Iso A is an 80/20 blend of 2,4- and 2,6-toluene diisocyanate,respectively.

Cat A is DABCO 33LV, a tertiary amine polyurethane catalyst.

Cat B is a 4 percent solution of calcium naphthenate in odorless mineralspirits.

NIAX A-1 is bis(N,N-dimethylaminoethyl)ether in dipropylene glycol, ablowing catalyst.

DC-5043 is a silicone surfactant available from Air Products.

NIAX C-225 is a blend of acid blocked 33 percent solution of triethylenediamine in dipropylene glycol and NIAX A-1.

FOMREZ UL-1 is dibutyltin dimercaptide.

PROCEDURE A

The following charges were employed to make the Macromer A:

2,000 parts Polyol A; 30.6 parts maleic anhydride; 96 parts of ethyleneoxide; 10 parts of Catalyst B (200 ppm calcium).

A three-liter, round-bottom flask with a stirrer, thermometer and gasinlet was charged with Polyol A, maleic anhydride and Cat B. Thecontents were heated to 125° C. and allowed to react for one (1) hour.This intermediate was transferred to a one-gallon steam heated stainlesssteel autoclave. After heating to 125° C. and pressurizing the reactorto 34 psig with nitrogen, ethylene oxide was added during one hour andthe mixture was reacted for eight hours. The product was discharged fromthe reactor and the volatiles stripped at 105° C. for one hour at <10 mmHg. This isolated product is designated as Macromer A.

EXAMPLE 1

Charges: To reaction flask.

Stream #1: acrylonitrile as indicated; styrene as indicated;2-hydroxyethylmethacrylate (HEMA) as indicated; 1-dodecanethiol-18.6grams.

Stream #2: Macromer A as indicated; Polyol C. as indicated; VAZO 67--9.3grams.

As the process was a continuous polymerization, 600 grams of graftPolyol B was added to a one-liter, 4-neck flask reaction flask fittedwith a stirrer, nitrogen inlet, addition tube, water condenser, andthermowell, having a discharge tube on the underside of the flask, andheated to 115° C. to begin the process. The contents of the reactorflask were stirred at 300 rpm and kept at 115° C. throughout thereaction. After heating the Polyol B in the flask to 115° C., Stream #1and Stream #2 were simultaneously charged to the reaction flask, whilethe contents of the reaction flask were permitted to discharge, so thatthe rate of charge and discharge corresponded to a turnover rate of 600ml/30 minutes. About seven (7) reactor turnovers were made with only thelast 600 ml collected and vacuum stripped at 125° C. and <2 mm Hg. Theweight percent of the monomer in the graft dispersion polyol was basedon the stripping loss of the last 600 ml collected. The total amounts ofeach charge and the physical properties of the graft polyol dispersionare reported in Table 1 below.

The same procedure was followed with respect to Samples 2-4, differingonly the type and amount of monomer charged. In Samples 2-3,2-hydroxymethylmethacrylate was charged in the amounts indicated; and inSample 4, no third monomer was charged. For each new sample, 600 ml ofthe previous sample was placed in the reactor flask to start thecontinuous process of polymerization.

                                      TABLE 1    __________________________________________________________________________                                                    WEIGHT                                              PERCENT VINYL    SAM-        POLYOL        AN    St    ACRYLATE    FEED  POLYMER  VISCOSITY    PLE C     MACROMER A                      (g)                         (%)                            (g)                               (%)                                  HEMA  HEA   TIME (min.)                                                    (calc.)  mPas/25C.    __________________________________________________________________________    1   2685.6               74.4   372                         30 744                               60       124 g (10%)                                              208   28.5     3100    2   2685.6              74.4    372                         30 744                               60 124 g (10%) 208   28.7     3010    3   2685.6              74.4    372                         30 620                               50 248 g (20%) 207   28.6     2940    4   2685.6              74.4    413.3                         33.3                            826.7                               66.7                                  0           210   28.8     3090    __________________________________________________________________________

EXAMPLE 2

Foam samples were prepared to measure the effect of each polyol on thefoam shrinkage. The following foam formulation was employed to prepareeach foam sample which corresponds to the graft polyol sample in Table1: 61.34 grams of graft polyol, 18.66 grams Polyol D, 120 grams PolyolC., 8.0 grams water, 2.0 grams diethanolamine, 2.6 grams DC-5043, 0.75grams Catalyst A, 0.2 grams NIAX A-1, and 92.2 grams of Iso A at anindex of 100. The foam ingredients were handmixed and poured into a10"×10"×4" aluminum mold preheated to about 150° F., allowed to react,and demolded. The foam shrinkage was measured by placing a straight edgefrom one corner of the foam block to the opposite corner and across thedeepest point of a depression in an uncrushed foam block. The distancein millimeters from the deepest part of the depression to the bottom ofthe straight edge was measured. The procedure was repeated for theopposite side of the foam block. The smaller the number, the lessshrinkage the foam had undergone. The results are reported below inTable 2.

                  TABLE 2    ______________________________________                                       FOAM                                       INDENTATION    FOAM   GRAFT     AIR       DENSITY TOP/BOTTOM    SAMPLE SAMPLE    FLOW (a)  (pcf)   (mm)    ______________________________________    1      1         2.08      2.28     14/15    2      2         0.63      2.24    2/0    3      3         2.80      2.40    0/0    4      4         1.30      2.33    15/17    ______________________________________     (a) = CRUSHED.

The results indicate that foam samples 1 and 4, made with graft polyolshaving a third monomer outside the scope of the invention or having nothird monomer at all, exhibited shrinkage, while foam samples 2 and 3,made with a graft polyol having a third monomer within the scope of theinvention, show a marked improvement in dimensional stability.

PROCEDURE B

The same procedure as employed in Procedure A was used to prepareMacromer B, the following charges: 2,000 parts Polyol F; 30.6 partsmaleic anhydride; 96 parts ethylene oxide; 10 parts Catalyst B (200 ppmcalcium). The product was designated as Marcromer B.

EXAMPLE 3

Charges: To reaction flask.

Stream #1: Acrylonitrile as indicated; styrene as indicated;dimethylaminoethylmethacrylate (DMAEMA) as indicated; reaction moderatortype and amount as indicated.

Stream #2: Macromer B--49.6 grams; Polyol type and amount as indicated;VAZO 67--9.3 grams.

The same procedure as employed in Example 1 was used for this example.The reaction conditions were as follows: total addition time of monomersStream #1:210 minutes; total addition time of Stream #2:210 minutes;turnover rate of 600 ml/30 minutes, reaction temperature 115° C. (Sample8 at 125° C.); stirred at 300 rpm. The amounts and types of otheringredients are reported below in Table 3. As in Example 1,600 ml of thesame or a similar graft polyol was used to start the continuous process.

                                      TABLE 3    __________________________________________________________________________    CARRIER POLYOL    SAMPLE         POLYOL              POLYOL                   POLYOL                        MACROMER                               AN        ST    GRAFT         D    C    E    B      GRAMS                                    PERCNT                                         GRAMS                                              PERCNT    __________________________________________________________________________    5    2710.4    --   49.6   558  40   620  50         (g)    6    2710.4    --   49.6   372  30   744  60         (g)    7    --        2710.0                        49.6   826.7                                    66.6 413.3                                              33.3                   (g)    8    --   2620.7                   --   49.6   413.3                                    33.3 826.7                                              66.6              (g)    __________________________________________________________________________                   RX MOD               WEIGHT                   1-            VISCOSITY                                        PERCENT    SAMPLE         DMAEMA    DODECANE                           MORPHOL                                  mPas.  VINYL                                              OH    GRAFT         GRAMS              PERCNT                   THIOL   INE (a)                                 25C.   (calc.)                                              (calc.)    __________________________________________________________________________    5    62   10   12.4    --    2800   25.58 25    6    124  10   12.4    --    2720   27.84 25.3    7    0    0    --      12.4  3880   27.92 115.8    8    0    0    12.4    --    4970   27.96 25.2    __________________________________________________________________________

EXAMPLE 4

Foam samples were prepared from graft polyol samples 5-8 to measure theeffect of DMAEMA on foam shrinkage. The following foam formulation wasemployed: Blending Polyol D with a graft polyol to yield 12 percentvinyl solids based on the weight of the mixture of Polyol D and thegraft polyol water--4 pbw, diethanolamine-1.5 pbw, NIAX C-225--0.7 pbw,FOMREZ UL-1--0.015 pbw, DC-5043--1.5 pbw, and Iso A in an amountsufficient to react at an index of 100. The foam ingredients were mixedand poured into a preheated aluminum mold, allowed to react, and testedin an uncrushed state as in Example 2. Foam Sample 5, using graft sample5, was 0/0 mm; Foam Sample 6, using graft polyol sample 6, was also 0/0mm; Foam Sample 7, using morpholine as the reaction moderator, havingonly aciylonitrile and styrene in a 2:1 ratio without any DMAEMA, was38/43.2 mm; and Foam Sample 8, using 1-dodecanethiol as the reactionmoderator and having only acrylonitrile and styrene in a 1:2 ratiowithout any DMAEMA, measured 30/38 mm on top/bottom.

What I claim is:
 1. A stable low viscosity graft polymer dispersioncomprising from 25 to 60 weight percent based on the total weight of thepolymer dispersion for making a polyarethane foam of a mixture of atleast three ethylenically unsaturated monomers polymerized in thepresence of a reaction moderator and a free radical initiator in apolyol mixture initially containing less than 0.1 moles of inducedunsaturation per mole of said polyol mixture; wherein said mixture ofethylenically unsaturated monomers comprises acrylonitrile, styrene or4-methylstyrene, and an amninofunctional C₂ -C₆ alkyl methacrylate. 2.The polymer dispersion of claim 1, wherein the alkyl methacrylatemonomer comprises dimethylaminoethyl methacrylate.
 3. The polymerdispersion of claim 1, wherein the alkyl methacrylate monomer consistsof dimethylaminoethyl methacrylate.
 4. The polymer dispersion of claim1, wherein the amount of said alkyl methacrylate monomer is from 5weight percent to less than 50 weight percent based on the total weightof the mixture of ethylenically unsaturated monomers.
 5. The polymerdispersion of claim 1, wherein the amount of said alkyl methacrylatemonomer is from 10 weight percent to 25 weight percent.
 6. The polymerdispersion of claim 5, wherein said styrene or 4-methylstyrene ispresent in an amount of 40 weight percent to 80 weight percent, based onthe weight of the monomer mixture.
 7. The polymer dispersion of claim 1,wherein the induced unsaturation is obtained by reacting apolyoxyalkylene polyether polyol with a compound having both ethylenicunsaturation and a hydroxyl, carboxyl, anhydride, isocyanate, or epoxygroup.
 8. The polymer dispersion of claim 1, wherein the inducedunsaturation is obtained by reacting a polyoxyalkylene polyether polyolwith a maleic anhydride and an alkylene oxide.
 9. The polymer dispersionof claim 1, wherein the viscosity of the dispersion is from 2000 to 5000cps at 25° C.
 10. The polymer dispersion of claim 1, wherein the polymerdispersion is white and has a monomer mixture content of from 25 weightpercent to about 50 weight percent, based on the weight of the polymerdispersion.